37,024 reputation
53482
bio website
location Vienna, Austria
age
visits member for 3 years, 10 months
seen 17 mins ago

Random praise for me:

You might see some necro-like-bumps from me. I'm trying to slowly edit/delete all my HINT answers from the site. I am also trying to stay away from giving hint answers in the future.

The last 10 answers I've posted:

  1. Zero sets in Mrówka spaces (22-Nov-2014)
  2. Regarding functions on $\omega_1$ (10-Nov-2014)
  3. Possible behaviours of the cofinality-of-neighbourhood function for topological spaces $X$ that are connected. (6-Nov-2014)
  4. Example of a $T_1$ space that does not have the property that every compact subspace of $X$ is closed. (5-Nov-2014)
  5. Why wouldn't someone accept Gentzen's consistency proof? (15-Oct-2014)
  6. Consistency of restricted forms of Martin's Axiom with the negation of the Continuum Hypothesis (8-Oct-2014)
  7. Spaces where all compact subsets are closed (2-Oct-2014)
  8. Is there always an equivalent metric which is not complete? (24-Sep-2014)
  9. Mary Ellen Rudin's proof that all metric space are paracompact (3-Sep-2014)
  10. Operators on the family of all subsets of a topological space that maybe generates a base for these family. (28-Aug-2014)

Yes, my answer-posting rate has slowed to a crawl. But I am generally happier with the questions I've been answering (and the answers I'm giving).

(Avatar image adapted from Lun-Yi Tsai's Surprised Again on the Diagonal, as found here.)


4h
revised Order topology on a subset may be weaker (but never stronger) than the subspace topology
deleted 8 characters in body; edited tags; edited title
4h
comment Converse of the Uryshon metrization theorem
All metric spaces are regular (in fact, perfectly normal), so the last sentence of the second paragraph is somewhat superfluous.
5h
revised Characterisation of the order topology on a linearly ordered set
deleted 37 characters in body; edited tags; edited title
10h
comment Density character of a metric subspaces
If by "$D \subseteq_{\text{dense}} K$" you mean "$D$ is a dense subset of $K$", then what you call the density character of $K$ is more commonly called simply the density of $K$, and is denoted $d(K)$.
1d
revised What is a “supplementary subspace”?
please don't use MathJax for formatting text
Jan
25
revised How were 'old-school' mathematics graphics created?
edited tags
Jan
25
revised About teaching an advanced principle mainly with pictures.
edited tags
Jan
25
revised Beautiful Mathematical Images
edited tags
Jan
25
revised Ways to project arbitrary Fractals on 2D objects and 3D objects w different dimensions?
edited tags
Jan
25
revised Magic theorem for cylinders? Symmetry classes according to Conway's notation?
edited tags
Jan
25
revised Mathematical places to visit
edited tags
Jan
24
comment How to find a limit like infinity to the power of negative infinity?
@MartinSleziak This user is unregistered and has not been seen since the day this was posted. It's probably a lost account, and will never return. Probably best to just judge whether it should be kept at all.
Jan
24
revised What is $[1, 5] \cap [4, 5[$?
deleted 32 characters in body; edited tags; edited title
Jan
24
revised Determining $\bigcap_{n=1}^{\infty}[-n,3^{-n}]$
added 24 characters in body; edited tags; edited title
Jan
24
revised Whats the difference between modular forms of different levels?
deleted 139 characters in body
Jan
22
revised The set of all exterior points is an open set
added 50 characters in body; edited tags; edited title
Jan
20
comment Any book on timeline of progress of Math concepts and applications
This question was subsequently cross-posted to hsm.SE.
Jan
18
comment Clarification on intuition behind one to one correspondence?
It might be helpful to mention which book is "your book".
Jan
18
comment Is there a more elegant way of proving $\langle (1,2)(3,4), (1,2,3,4,5) \rangle = A_5$
Your comment and your answer seem to be at odds with each other. When you write $(a,b) = (1,a)(1,b)(1,a)$, you are not writing $(a,b)$ as a 3-cycle, but rather writing $(a,b)$ as a product of three transpositions (2-cycles).
Jan
18
revised Nipotent matrix over a ring
removed rant